Production of carbamates of the alkali-forming metals



Patented Dec. 4, 1934 Q PRODUCTION CARBAMATES OF THE ALKALI-FORMING METALS Robert Burns MacMullin and Wesley King McCready, Niagara Falls, N. Y., assignors to The Mathieson Alkali Works, Inc., New York, N. Y.,

a corporation of Virginia No- Drawingf Application June 4,1932, v

Serial No. 615,464

li -Claims. (Cl. 260-112) .This invention relates to improvements in the monium carbamate is easilyseparated from the production of carbamates of the alkali metalsand product, by volatilization in a current of; dry air the alkaline earth metals. One conventional for example. The ammonium chloride dissolved method of producing these carbamates is toprein the aqueous ammonia solutioncan be recovered .5 cipitate the carbamate from a liquid ammonia byevaporation. Other salts useful for the pro- 6Q solution of a soluble salt of the metal by the induction of sodium carbamate include sodium brotroduction of carbon dioxideunder appropriate mide, .sodiumiodide and sodium nitrate. The conditions. Theicarbamates of the alkali metals carbamates of potassium and lithium and of caland the alkaline earth metals areverysoluble in cium, barium and magnesium can similarly be 10 water and, as a consequence,- the absence of water produced from the bromides, chlorides, iodides and has been regarded as important to efiicient renitrates of these metals. The water present durcovery of these carbamates. On the other hand, s h i n y W adVanl/age, range from the available salts of the alkali metals and the about 5% to about 100% by Weight of the amalkaline earth metals are in general moresoluble monia. r a

.15 in ammonia in the presence of Water than in an- In carrying out the invention to embody both hydrous ammonia. Thisinventionprovides modmodifications, carbondioxide and a soluble salt ifications of this conventional method which, inof the metal to be produced are brought tostead of beinghampered by take advantage of gether in thelprese nce of water, a liquid miscible these facts and which afiord several important in Water but in which the carbamate to be pro- 20 advantages. a I duced is less soluble than in water, and ammonia, The first modification of this invention comand the metal carbamate is separated from the prises the addition of water to the usual reactants, resulting solution, Ethyl alcohol, methyl alcoammonia, carbon dioxide and a soluble salt of hol and acetone are particularly useful as diluents the metalof the carbamate to be produced. The of theaqueous ammonia solution in which the re- 25 second modification. comprises, in conjunction action is effected. Such diluents may be added with the first, the addition of a liquid miscible in proportions-ranging from about 50% to about with water. but in which the carbamate to be 200% by weight of the water. The sequence in produced is less soluble than in water to the usual which the reactants are brought together is not reactants. .Thefirst modification operates, in genimportantg For example, the metal salt may be 30 eral,q;to increase the ,solubility ofthe salt of the dissolved in the aqueous alcohol solution, the

metal of the carbamate to be produced in the reammonia added to this solution and the resultaction mixture, and also to reduce the vapor presins Solution carb at d, the metal Salt may be sure of the reaction mixture, and the second moddissolved in the aqueous alcohol solution and the ification operates to decrease the solubility of the ammonia and Carb d d then added together 35; metal carbamate in the reaction mixture. as such or in the form of a compound such as 9 In carrying out the invention to embody the ammonium carbamate, or the metal salt may be first modification, carbon dioxide and a soluble dissolved in water, the ammonia and carbon disalt of the metal of the carbamate to be prooxide added to this solution and the alcohol then duced are brought together in the presence of added to the resulting Solution.

$9; water and ammonia, and the metal carbamate is The following exa p W illustrate the separated from the resulting solution. In the provention: duction of sodium carbamate, for example, a so- Example 1 lution of ammonia in water, containing about 4 parts (by weight) of Sodium hlo id are 50% by weight of each, is Saturated With Sodium added to a mixture of 54 parts of ammonia and chloride and this solution is carbonated at 8.1)011'5 6 parts of water, and carbon dioxide is then lmder superatmosphelic Pressura Sodium passed into the mixture until 3 parts have been Carbamate, Ha is precipitated, the absorbed. The reaction mixture is brought to a monium chloride formed in the reaction dissolvtemperature of b t 20 3, d the crystalline n n e aqu us ammonia 80111151011- The p sodium carbamate formed is separated by filtracipitated sodium carbamate is separated from the t A yield of about 5.7 parts of pure sodium 5 aqueous ammonia solution, by filtration for exb at i bt i d; ample. This separated sodium carbamate may be contaminated with some ammonium 'carba- Example 2 mate, by the introduction of an excess of carbon 11 parts of sodium chloride are added to a mix- 1 dioxide for example. Such contaminating amture of 52 parts of ammonia and 22 parts of 1 water, and carbon dioxide is then passed into the mixture until 8.2 parts have been absorbed. The reaction mixture is brought to a temperature of about 20 C. and the crystalline sodium carbamate formed is separated by filtration. A yield of about 14 parts of pure sodium carbamate is obtained.

Example 3 10 parts of sodium chloride are stirred into a mixture of 24 parts of ammonia, 11 parts of carbon dioxide, 40 parts of water and 50 parts of ethyl alcohol while maintaining the reaction mixture at a temperature of about 30 C., The crystalline sodium carbamate formed is separated by filtration. A yield upwards of about 10 parts of pure sodium carbamate is obtained.

In carrying out the invention to embody the second modification, a double salt, sodium ammonium carbonate, will form either with or to the exclusion of the metal carbamate, if either the diluent concentration or the temperature is too low. 'With ethyl alcohol as the diluent, for example, it is advantageous to bring the reactants together at a temperature above about 20 C. and to have the ethyl alcohol present in proportion approximating 100-200% by weight on the water.

In conjunction, the two modifications of the invention make possible the production of a product of particularly desirable crystalline form, the crystals being usually much larger than those produced by precipitation from anhydrous liquid ammonia in the conventional manner. Using but the first modification of the invention, a substantial excess of ammonia is usually desirable to stabilize the metal carbamate while in contact with the water; this requirement is eliminated or reduced by the second modification of the invention. In general, it is desirable to use at least a slight excess of both ammonia and carbon dioxide and to have the ratio of ammonia to carbon dioxide at least 2: 1.

The chloride of the metal of the carbamate to be produced is a particularly desirable raw material since by the use of the chloride the process of the invention becomes a process for the production of ammonium chloride as well as for the production of the metal carbamate.

We claim:

1. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, a diluent liquid miscible with water but in which the carbamate to be produced is less soluble than in water, and ammonia, carbon dioxide and a soluble salt of the metal, water being present in proportion approximating 5%-100% by weight of the ammonia, and separating the metal carbamate from the resulting solution.

2. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, methyl alcohol and ammonia, carbon dioxide and a soluble salt of the metal, and separating the metal carbamate from the resulting solution.

3. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, ethyl alcohol and ammonia, carbon dioxide and a soluble salt of the metal, and separating the metal carbamate from the resulting solution.

4. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, acetone and ammonia, carbon dioxide and a soluble salt of the metal, and separating the metal carbamate from the resulting solution.

5. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, ethyl alcohol and ammonia, carbon dioxide and a soluble salt of the metal, at a temperature above about 20 C., ethyl alcohol being present in proportion approximating 100-200% by weight on the water, and separating the metal carbamate from the resulting solution.

6. In the production of carbamates of the alkali forming metals, the improvement which comprises bringing together, in the presence of water, a diluent liquid miscible with water but in which the carbamate to be produced is less soluble than in water, and ammonia, carbon dioxide and a chloride of the metal, water being present in proportion approximating 5%-100% by weight of the ammonia, and separating the metal carbamate from the resulting solution.

ROBERT BURNS MACMULLIN. WESLEY KING MCCREADY. 

